Rihanna gives painful details of Chris Brown assault

In a "20/20" interview airing Friday, Rihanna offers her graphic account of the fateful February 7 confrontation with then-boyfriend Chris Brown - including the terrifying blankness that seemed to come over him as he assaulted her.

She said all she kept thinking was, "When is it going to stop? When is it going to stop? He had no soul in his eyes. Just blank. He was clearly blacked-out. There was no person when I looked at him."

The fight, she said, started when Brown received a text message from another woman while they were driving away from a Grammy Awards party.

"I caught him in a lie, and he wouldn't tell the truth. And I wouldn't drop it," Rihanna told Diane Sawyer in the interview, portions of which aired Friday morning on "Good Morning America."